Microbiological and Physico-chemical Study of Swimming Pool Water

Swimming pools are places that must be constantly evaluated to avoid health problems for the users. The aim of this study was to evaluate the microbiological and physicochemical quality of swimming pools in the Metropolitan Area of Mexico City. Seven swimming pools were sampled during two periods; the pH and dissolved oxygen of each one was determined in situ. Two samples for microbiology were taken in sterilized bottles, one previously dechlorinated with sodium thiosulphate, the other for physicochemical determinations. In the laboratory, we determined free-living amoebae (FLA) by isolation in selective culture medium and morphological identification, Pseudomonas aeruginosa, total and fecal coliforms, residual free chlorine, turbidity, color, total alkalinity, total hardness, ammoniacal nitrogen, dissolved solids and conductivity according to the standard water analysis methods of the APHA, AWWA, WEF (2012). Bacteriologically, all the swimming pools were within the norm for fecal coliforms, however, Pseudomonas aeruginosa was found in three pools (AzA, At and GAM). Five species of FLA were isolated, of which Acanthamoeba polyphaga is the only one reported as a potential pathogen. The isolated strains of this amoeba presented different degrees of pathogenicity. This is important because Acanthamoeba is an opportunist amoeba that can cause disease in patients with low defenses, therefore swimming pools must undergo careful chlorination and cleaning. Turbidity was within the Official Mexican Standard NOM-245-SSA1-2010 in all pools. Levels of pH were within the limits of the Standard in all pools with the exception of At and TC, in the second period. However, residual free chlorine, only one swimming pool, TB, fell within limits in both periods and AzA, TC and GAM only in one period. In general, the swimming pools presented good microbiological quality, although some were outside the norm in physicochemical quality, some for having excess free chlorine and one for having very pH acid, which could compromise the health of the user